Physical Sciences Research Highlights

The Contradictory Catalyst

Researchers find the key to speeding up the rate of reaction of a potential catalyst for energy storage lies in making the reactive parts of the catalyst move more slowly.

This synthetic catalyst uses an inexpensive metal at its core to produce hydrogen fast.
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One reason we can't bottle summer
sunshine and save the solar energy for rainy days is that we don't have an
efficient way to store it. Nature stores energy in chemical bonds, like when
plants photosynthesize our food. Researchers are trying to design catalysts
based on inexpensive metals to store energy like nature does.

The chemical bonds
in hydrogen gas, for example, could power fuel cells, internal combustion
engines or generators. Using a natural catalyst from bacteria for inspiration,
researchers have now developed the fastest synthetic catalyst for hydrogen
production -- producing 45 million molecules per second. Instead of a costly
metal, this catalyst uses inexpensive, abundant nickel at its busy core.

Why It Matters: Although the
catalyst requires more energy to run than a conventional platinum catalyst, the
insight garnered from this result might eventually help make hydrogen fuel in
an environmentally friendly, affordable way, the researchers report in the
chemistry journal Angewandte Chemie
International Edition.

Molly O'Hagan explores different catalysts inspired by nature, looking for one that runs fast and efficiently.
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"The next
thing we'll work on is making it more efficient," said chemist Molly
O'Hagan at the U.S. Department of Energy's (DOE's) Pacific Northwest National
Laboratory. "We still have to feed it too much electricity to produce the
hydrogen."

As they worked
on the catalyst development, the scientists would test their catalysts in
reactions by combining the catalyst and acids in different media. One thing
they noticed was that the synthetic catalyst produced hydrogen faster in a
viscous liquid as opposed to a free-flowing liquid.

"We used
this medium that was like pancake syrup and saw very fast rates," said
O'Hagan. "The catalyst has arms that move around to position the pieces of
the chemical reaction. Normally they are flopping around like crazy and the
pieces don't always hit the right target. When this happens, the arms can
actually get stuck in a position where the catalyst can't put the pieces
together at all. We thought that this thick syrup might be slowing down the
flopping, letting the arms put the pieces together more efficiently."

To test this
hypothesis, the team designed the catalyst to have longer arms that would drag
and slow down the flopping. They tested different arm lengths and found the
longer the arms, the faster the catalyst produced hydrogen molecules.

They also measured
how fast the arms were swinging around. The longer the arms, the slower the
movement, allowing them to attribute the faster hydrogen production to the
slower arm movements. Like excited children playing catch, calming down a bit
lets them hit their mark more often.

"This work
gave us some insight into the movement of the catalyst, and how to control that
movement to make it more efficient," said O'Hagan.

What's Next? This work is part of ongoing studies
at the Center for Molecular Electrocatalysis, a DOE Office of Science, Office
of Basic Energy Sciences, Energy Frontier Research Center.

Acknowledgments

Sponsor: This research was supported as part of the Center for Molecular
Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department
of Energy, Office of Science, Office of Basic Energy Sciences

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In short...

In 100 characters: Slowing the reactive arms of a catalyst for energy storage makes it go faster

In one sentence: Researchers at the Center for Molecular Electrocatalysis find the key to speeding up the rate of reaction of a potential catalyst for energy storage lies in making the reactive parts of the catalyst move more slowly.